Courtesy is the required manner or standard of behaviour expected in a Court of the Crown.
It is the expression of humbleness & deference to a higher authority by people with status.
Common courtesy is the manner expected of common people when in the presence of nobility or royalty.
Courtesy is hierarchical and one directional.
Nobility expects the presence of courtesy to each other in deference to their monarch.
They do not expect the Nobility to extend common courtesy to those of a lower status or rank.
The Common Man is rarely offered common courtesy by uncommon people.
Courtesy has never been a measure of authority, more an expression of status.
In reality, the higher the authority a person believes that they have, the less courteous they believe that they have to be.
Unless that is they are in the presence of Royalty or in a Royal Court.